1. Field of the Invention
The present invention relates to an optical fiber and power line composite cable that is installed in a section between base station equipment and an antenna included in a mobile telecommunication base station and that includes optical fiber units and power line units to transmit a mobile telecommunication signal and power, and more particularly, to an optical fiber and power line composite cable that includes a protective metal layer surrounding optical fiber units and power line units and that is capable of preventing the power line units or the optical fiber units from moving inside the protective metal layer when the optical fiber and power line composite cable is vertically installed, compared to the related art.
2. Background Art
In the case of conventional mobile communications, communication signal is transmitted to a base station from a backbone station of a telecommunication company or the like, and a radio-frequency (RF) signal is transmitted from a base transceiver station (BTS) of the base station via an antenna of the base station. A radio signal transmitted from a user's mobile phone is transmitted to the antenna of the base station, amplified through a tower mounted amplifier (TMA), and then supplied to the BTS. In this case, the base station, the TMA, and the antenna are connected via a coaxial feeder.
However, the longer the length of a cable, the greater signal loss in the coaxial feeder. When the antenna is installed at a tower having a height of several tens of meters, signal loss occurs in the coaxial feeder that connects the antenna and the base station installed on the ground. Since the signal loss occurring in the coaxial feeder causes a signal supplied from the base station to have an intensity that is less than signal intensity required in the antenna, the supplied signal attenuates. Thus, the supplied signal needs to be amplified by the degree to which the signal attenuates in the coaxial feeder, thereby causing additional power consumption. Also, since the intensity of a signal transmitted from a mobile phone to the antenna of the base station is relatively low, it is very difficult to transmit the signal to the BTS via the coaxial feeder causing high signal loss. Accordingly, it is necessary to install a TMA at an input unit of the antenna to amplify the attenuating signal. However, since the TMA consumes a relative large amount of power to amplify the signal, high costs are incurred to perform maintenance and repair, thereby lowering system efficiency.
A remote radio unit (RRU) has been introduced to compensate for the high power consumption and inefficient maintenance and repair of the telecommunication base station using the TMA. The RRU separates an RF unit (RU) from the conventional BTS, disposes the RU on a base station tower, and remotely controls the RU. Here, RRU equipment and the remaining BTS from which the RU is separated, i.e., a baseband unit (BBU), are connected via an optical cable in which signal attenuation hardly occurs, and a power supply cable is additionally used to supply power to the RRU. Also, since the RRU is installed on the base station tower together with the antenna of the base station, the length of the coaxial feeder that connects the antenna of the base station and the RU may be minimized and the TMA need not be installed. Thus, signal amplification need not be additionally performed for a signal that attenuates in the coaxial feeder, and the efficiency of maintenance and repair performed by the base station increases. Here, an optical fiber and power line composite cable manufactured by combining an optical cable and a power supply cable is used to minimize the number of cables to be installed.
As described above, when the optical fiber and power line composite cable is installed between base station equipment and the antenna of the base station in the mobile telecommunication base station to simultaneously supply power and an optical signal, a metal layer is formed to accommodate a cable core including optical fiber units and power line units of the optical fiber and power line composite cable. However, in the related art, the cable core is surrounded with a metal layer having no corrugations or a having a corrugated tape form. In this case, when the optical fiber and power line composite cable is vertically installed, the power line units or the optical fiber units are likely to move inside the metal layer.